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# 9Sci CH7

### 9th Science CH7 Machines-Making Work Easier

TermDefinition
bionics the science of designing artificial replacements (prostheses) for parts of the human body that are not working properly
compound machine a combination of two or more simple machines
efficiency the ratio of the useful work put out by a machine to the work put into that machine; efficiency is always less than 100 percent
effort arm the part of a lever on which an effort force is applied
effort force the force applied to a machine, when a machine is used to do work
fulcrum the fixed point around which a lever pivots
ideal machine a machine in which work input equals work output; such a “perfect” machine would be friction-less and 100 percent efficient
inclined plane a simple machine consisting of a sloping surface (ramp) used to raise objects
lever a simple machine consisting of a bar that is free to pivot (rotate) around a fixed point (fulcrum)
machine a device that makes work easier by changing the size of the force applied to it and/or the direction of that force
mechanical advantage the number of times a machine multiplies the effort force applied to it
power the measure of the amount of work done in a specific amount of time; power is measured in watts and equals 1 joule/second
pulley a simple machine consisting of a grooved wheel with a rope or chain running along the groove
resistance arm the part of a lever that exerts the resistance force
resistance force the force exerted by a machine to overcome resistance to gravity or friction
screw a simple machine consisting of a special type of inclined plane wrapped in a spiral around a cylindrical post
simple machine a device that accomplishes work with only one movement; the lever, pulley, wheel and axle, inclined plane, screw,and wedge are all simple machines
wedge a simple machine consisting of a moving inclined plane with one or two sloping sides; examples are knives and chisels
wheel and axle a simple machine consisting of two different-sized wheels that rotate together, such as a doorknob